Note: Descriptions are shown in the official language in which they were submitted.
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BANK NOTE VALIDATOR
Description
Background of the Invention
The present invention relates generally to a bank note validator and more
specifically to a bank note validator designed to distinguish between
authentic documents
and counterfeit documents.
Currency validation is most popularly used in connection with a product or
service. With the ever increasing demand on entrepreneurs for increased sales
and for
increased financial transactions, innovative methods are required to maintain
growth.
Bank note acceptors have answered the call of the marketers, by providing the
ability to
facilitate high cost transactions mechanically. Bank note validators are most
popular in
the beverage vending food vending, product vending, gaming and wagering
businesses.
Change machines, i.e., currency to coin facilitating beverage, phone, and many
other
transactions are popular. In addition, bank note or cun;ency validators are
also used to
authenticate such other financial instruments as stocks, bonds, and security
documents.
Therefore, as used herein, the term "bank notes" or "notes" will encompass all
such
applications.
Most bank notes, or notes, are quite mutilated and defaced prior to being
removed
from service. Prior to the removal from service the notes are legal tender and
are
expected to be used in transactions. The known bank note validators have a
difficult
time of validating mutilated and worn notes. The acceptance of such legitimate
notes is
always less than one hundred percent in a currency validator. Counterfeit
elimination is a
very demanding requirement. Simply stated, all nongenuine notes presented to
the bank
note validator must be automatically rejected, regardless of the origin. Even
counterfeit
documents which have not yet been developed are expected to be detected and
rejected
when they appear.
Most bank note validators have been designed targeting generalized markets,
and
the industry has permitted reduced performance in one or more sensing areas,
in favor of
the more economical approach of one size fits all. Unfortunately, most end
user
applications are very different, and one size does not fit all. In fact,
beverage vending or
music machine product losses are not even comparable with those of change
machines,
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postal systems, or ATM applications. Yet often the criteria for usage is the
cost of the
system. Bank note validator manufacturers compete in applications where their
machines perform with the best fit for the customer. Often nonperforming
machines are
permitted to enter the marketplace where there is no bonafide means of
performance
quality testing, and the quality performing machine manufacturers are usually
forced to
provide extra service or price cuts to maintain sales.
By far, bank note validation has been most popular in the United States, with
the
introduction of the beverage vending validator. These validator systems were
simple, yet
efficient. The major fault was with the technology implemented in the
validation process.
Each and every manufacturer fell prey to the casual counterfeiter. As the bank
note
validator proliferated throughout many types of applications, the demands for
better
systems became even greater. Original systems relied on the magnetic
information
inherent in genuine U.S. currency and a few foreign countries. But this
technique is
highly susceptible to the modern copy machine. Most offices, and libraries in
the United
States have black and white copy machines, and most everyone has access to
one.
Optical systems began to be employed with the intent of improving security.
These
systems generally work on some type of image analysis technique. They are
susceptible
to having poor performance with worn and mutilated notes as well as extremely
new
notes. Most bank note validators employ both optical and magnetic systems in
an effort
to gain maximum validation performance and security.
In systems where magnetics are used, it is not uncommon to have a note
designed
with the narrowest stripe possible which will defeat the system. In optical
systems, the
image of a note is easily reproduced with modern photocopying techniques.
Often the
image is enhanced in specific areas to specifically fool the bank note
validator.
Bank notes worldwide share at least one thing in common: none are immune from
counterfeiting. Casual counterfeiting with facsimiles is on the rise with
increased
accessibility to technology. Also on the rise is the demand for currency
systems.
By far the greatest advancement in the bank note validator has been with the
implementation of optical systems. The optical devices have been used
transmissively
and reflectively. Optical systems are very good at analyzing currency, since
all bills are
designed to be recognized on sight by humans. Many features such as
watermarks,
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security threads, and colored threads inserted as counterfeit deterrents are
detectable
primarily by sight. Therefore it is reasonable to understand why people have
high
expectations towards electronic vision systems. Unfortunately the human model
for
counterfeit detection cannot be built electronically into bank note validation
systems
because the cost would be prohibitive. A common method employed is to measure
the
signal responses reflected, or transmitted through the printed and non-printed
areas on
the surface of a bank note, utilizing common light sources and comparing the
result with
an image stored in the currency validator memory. Major difficulties are
encountered
with detecting properly the very new bank note, and the degraded image
resulting from
the worn bank note, compounded by printing misregistrations, while rejecting
the
acceptance of counterfeits.
In the performance of spectral analysis it is possible to characterize the
reflective,
transmissive and absorptive properties inherent in genuine bank notes. With
light of
wavelengths narrowly focused between ultraviolet and infra red. It is possible
to
determine the chemical composition of bank notes, as is employed in scientific
analysis
of other chemical studies, and store the results in a database for comparison
later. In fact,
utilizing the strictly controlled "chemical signature" of bank notes would be
just the thing
to detecting frauds and counterfeits. However, to implement a spectrum
analyzer in the
bank note validation system would be prohibitive in both terms of expense and
time
required to perform a scan of the full light spectrum for each point along the
length of a
bank note.
The spectral analysis approach is not necessarily a fine resolution type
system
relying on the printed image of the bank note. It is a system which relies on
the
"signature bands" of genuine bank notes as they are generated by the
absorbance,
reflectance and transmission of specific wavelengths of light. A single
detector is
employed with several Light Emitting Diodes (LED's) modified (filtered) in
such a way
that only a specific wavelength of light (~) a tolerance (say 5 manometers),
is emitted by
each LED. The common detector measures the effect of reflectance or
absorbance,
transmittance of the bank note to each LED individually and combined. Thus
creating a
signature of the bank note as it responds to various narrow wavelengths of
light reacting
on a single area of the note as measured by a single detector, the system as
described
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would provide the most benefit if employed as an array of such subsystems,
facilitating
maximum security and resistance to the striping of authentic bank notes.
Validation techniques have been consistently foiled by the ability of
individuals
to replicate the features inherent to bank notes, with engineered facsimiles.
The casual
counterfeiter has at their disposal a variety of tools which are sufficient in
generating
reasonable facsimiles to foil even the best Currency Validator. Copy Machines,
black
and white, color copiers, fax machines, ink jet copiers, computers and
scanners are all
tools which may be used to foil the common bank note validator. Some of these
methods
are very detailed and complex, yet, none utilize the exact chemistry found in
engraving
dyes and inks used in bank note printing.
Current bank note validator technology typically uses one or more optical
sensors
to detect the optical reflection and or absorption characteristics of bank
notes. Many
systems incorporate emitters and detectors operating in 2 or more wavelengths.
These
units usually take several points in discrete paths or channels along the long
axis of a
bank note. By comparing the sampled results with pre-stored results from real
bank
notes, a determination can be made as to the type and genuineness of the bank
note.
Typically the emitter/detector pairs comprise at least one set of infrared
sensitive
units. This allows data to be taken for almost all currencies, regardless of
the visible
color of the bank note. However a drawback to this method is that a two tone
copy
(black & white) or a copy made on colored paper can be devised that will
produce data
that mimics a real bank note, causing a counterfeit bank note to be accepted
as genuine.
As color copy technology has improved, it has also become possible to produce
color
copies almost identical in the visual spectrum with real bank notes.
Many countries constantly change their currency to limit counterfeit bank
notes,
cut production costs, improve longevity, etc. Several countries use different
width bank
notes as well. These different widths are difficult to accommodate in a single
validation
unit since the data channel for the narrower bank notes will vary depending on
the
insertion location in the unit. This usually requires several databases to be
developed for
one denomination. During the validation process it is necessary to scan each
of these
databases in succession, and then decide if a match is possible. This can
result in a
process that takes several seconds, annoying or worrying the user.
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Since most currencies in the world use different color combinations on
different
denominations, a validator that can detect these colors would be able to
select which
database to use to compare with the bank note. This would reduce the
processing time
significantly since only one set of databases needs searching. Two tone copies
might be
eliminated since there would be no color in the data collected. Copies printed
on color
paper could also be eliminated, since the subtle color variations on real
currency would
be missing. By comparing the color data with infrared data, acceptance of
color copies
may be greatly reduced.
Typical systems to detect color utilize three sensors for the Red, Green and
Blue
portions of the visible spectrum, and a white light to illuminate the object.
White light
sources that produce an even spectrum of light are usually expensive, bulky or
require an
exotic power supply. Each sensor has a filter to allow only a specific portion
of the
spectrum to pass. By combining the information from the three sensors, and
applying
mathematical equations to the data, the color of an object can be determined.
What all of the present bank note validators lack, and what is desirable to
have, is
the ability to quickly and accurately determine the authenticity of bank note
while
keeping the cost and size of the validator to a minimum. This longstanding but
heretofore unfulfilled need for a compact and relatively inexpensive bank note
vaiidator
that can quickly and accurately distinguish among authentic and counterfeit
bank notes is
now fulfilled by the invention disclosed hereinafter.
Summarv of the Invention
According to the present invention a bank note validator is comprised of a
detector to detect the light from LEDs reflected off of the surface and
transmitted through
a selected bank note to determine the authenticity thereof. The system
comprises four
emitters, a detector, and a programmable gain amplifier.
Full details of the present invention are set forth in the following
description and
in the accompanying drawings.
Brief Description of the Drawi~s
For a more complete understanding of the nature and objects of the invention,
reference should be made to the following detailed description, taken in
connection with
the accompanying drawings, in which:
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Fig. 1 shows schematically the current invention;
Fig. 2 shows schematically the function of the sensing units;
Similar reference numerals refer to similar parts throughout the several views
of
the drawings.
Description of Preferred Embodiment
The object of this invention is a method to determine the color of a bank
note,
simply, accurately, and inexpensively. This method utilizes a PIN diode
detector whose
spectral characteristics resemble the human eye.
Since the typical bill validator needs to be small and inexpensive, multiple
sensors and white light sources are not the preferred method of construction.
The current
embodiment of the invention utilizes different visible colored LED's to
illuminate the bill
and an IR detector with sensitivity in the visible spectrum. Four LED's--
namely, red,
green, blue and infrared, are arranged in such a manner as to shine on the
same fixed
point, are contained in the system. The detector is mounted to collect the
reflected or
transmitted light from the LED's.
In the present invention, photodiode 10 consisting of multiple LED's is
arranged
to selectively sense the light emission from the bank note being tested, as it
passes
through the validating section, of the bank note validator. The signal, i.e.,
the current
produced by the photodiode 10 from a selected LED is fed to a amplifier
section
generally depicted by the numeral 12, the operation of which, including the
sequencing
of the output from this section 12 is controlled by a computer control (CPLJ)
stage 14 for
analysis, display and determination of the validity of the bank note.
Dependant on the
results obtained, the bank note is either accepted or rejected.
Specifically, as seen in Fig. 2, the current from the photodiode, obtained
through
LED 18 is fed to a first step amplifier 20 where it is converted into a
voltage. The input
signal current is filtered by a capacitor 22 in the first stage to reduce
noise from external
sources. The amplifier 20 is a low offset voltage type to reduce any error due
to the high
gain of the circuit. Output from the first stage is input to the feedback pin
of a
multiplying D/A converter 24. The D/A in conjunction with a second amplifier
26
comprises a programmable gain stage, i.e., an amplifier whose gain can be
modified by a
microprocessor 28. The output at terminal 30 of the second amplifier 26, may
thus be
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balanced to the light or wavelength of a selected color, since each wavelength
of light
may be defined by a different gain setting, to balance the final output. A
final amplifier
stage 32 acts as an inverter and low pass filter (cutoff between lKhz and
above) to
reduce noise from external sources and prevent antialiasing of the signal at
the AID
converter. The output from the final or third amplifier 32 is passed via
terminal 34 to the
control CPU 16.
To take a sample, LED 18 is illuminated, the gain of the amplifier 20 is set,
and a
sample is taken at the output of the filter stage by an A/D converter 24. The
output from
the A/D converter if fed to the progranunable gain control re: amplifier 26
and processor
28, which is then sequenced through Red, Green, Blue and IR. The output being
then
stored in memory of the CPU for processing, display and control of the
validator
apparatus.
The arrangement shown in Fig. 1 utilizes four separate amplifier channels R,
G,
B for each LED color red, green and blue respectively and IR for the infra red
light.
These are pre-set non-programmable frequency amplifiers for each color
respectively. It
also requires associated gain and filter circuits, although, their operation
is essentially as
described with respect to Fig. 2 provides separate amplifier channels for each
LED color.
While comprising more parts, the gain of each stage could be set individually
in the
factory. This precludes the need for adjustment in the field by a highly
skilled
technician. From time to time the unit might require servicing as parts age,
although, this
is not a significant problem.
Therefore, the arrangement shown in Fig. 2, where the color output is
controlled
and balanced by the microprocessor 28 through a single amplifier/gain circuit
is
preferred. This arrangement eliminates separate amplifier for each color
reducing the
number of parts required and improves linearity of the system.
As mentioned previously, the present invention allows the use of either
reflective
or transmitted light to be detected. One reason for using transmitted light is
to assist in
compensating for the change in brightness of LED's due to temperature changes.
Validators are used in various environments from the Sahara Desert to
Greenland for
vending application. Temperature extremes of-25°C to +50°C are
not unknown. Each
LED's light output for a given current is proportional to temperature so that
as the
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temperature increases, light output decreases and vice-versa. In addition,
LED's made
from different processes respond differently. to temperature in varying
degrees. Suffice it
to say the Red, Green and Blue devices behave very different from each other
with
temperature variation. Since the present invention requires that the response
to white
light remain fairly constant, a machine adjusted to work in New York in
September, will
not function in the Sahara or Greenland.
To compensate for temperature variation, the programmable gain stage is
provided with a video adjustment sensor to monitor the LED brightness
constantly and
adjust the gain for each light color channel. When a video adjustment is made,
the
relative readings for the transmitted light is made for each such channel,
with no paper or
bank note between the LED's and the detector. These readings are stored in
memory. As
the validator waits for a bill to be inserted, the microprocessor monitors the
LED's and
modifies the gains to maintain them identical with the stored readings. This
maintains
the balance over the expected temperature variations. To adjust the unit a
special card is
inserted. This card has white, black, red, green and blue regions on it. As
each different
area passes under the sensor, the relative strengths of the responses are
measured. An
algorithm in the microprocessor then adjusts the D/A settings for each LED to
achieve
the proper balance.
It shall be noted that all of the above description and accompanying drawings
of
the invention are to be considered illustrative and are not to be considered
in the limiting
sense.
It is also understood that the following claims are intended to cover all of
the
generic and specific embodiments and features of the invention herein
described.
